Rectifenestella araxensis ( Nikiforova, 1933 ) Ernst & Senowbari-Daryan & Hamedani, 2006

Ernst, Andrej, Senowbari-Daryan, Baba & Hamedani, Ali, 2006, Middle Permian Bryozoa from the Lakaftari area, northeast of Esfahan (central Iran), Geodiversitas 28 (4), pp. 543-590 : 554-556

Rectifenestella araxensis ( Nikiforova, 1933) n. comb. ( Figs 4I, K, L ; 5 A-E; Table 10)

Fenestella araxensis Nikiforova, 1933: 15 , pl. 6, fig. 6. — Morozova 1970a: 172, 173, pl. 35, fig. 1.

LECTOTYPE. — Central Museum of Geological Prospecting, Saint Petersburg, Russia. Thin section No. 31, pictured in Nikiforova 1933: pl. 6, fig. 6 (designated by Morozova 1970a: 172). River Arax, Transcaucasia (Nakhichevan); Gnishik Horizon, Middle Permian, Murgabian (= Wordian).

MATERIAL EXAMINED. — 1-5-3, 2-3-4, 4-1, 4-14, 7-1-1, 7-2, 9-3, 9-5, 9-6-3, 11-2, 17-1, 20-1-1, 20-1-3, 23-1-3, 23-3-3, 23-8-4, 24-1-1, 24-3-2, 25-10, 26-2.

OCCURRENCE. — Transcaucasia (Nakhichevan), Gnishik Horizon, Middle Permian, Murgabian (= Wordian). Lakaftari: central Iran, Jamal Formation, Middle Permian.

DESCRIPTION

Micrometric formula: 20-28/13-19//20.5-26.5. Reticulated colonies with straight branches, joined by dissepiments. Bifurcation common. Autozooecia arranged in 2 alternating rows on branches, becoming 3 in places of bifurcation and occasionally between bifurcation areas at short distances. Apertures circular, spaced 2 per length of a fenestrule, containing 8 small nodes in the peristome shaping it as a regular octagon. Shape of fenestrules varying from oval to slightly rectangular. Keel low, carrying single row of moderately large and closely spaced nodes. Internal granular skeleton thick, well developed, continuous with obverse keel, nodes, peristome and across dissepiments. Outer lamellar skeleton moderately thick, containing abundant and closely spaced microacanthostyles 015- 20 µm in diameter. Microacanthostyles having distinct hyaline cores and dark sheaths.

INTERIOR DESCRIPTION

Autozooecia pentagonal in the middle tangential section, rhombic in the middle row, low and elongated, with well developed vestibule; aperture positioned at distal to distal-abaxial end of chamber. Superior hemisepta short; inferior hemisepta absent.

COMPARISON

Rectifenestella araxensis n. comb. differs from R. crassinodata n. sp. in having smaller and more closely spaced nodes of the keel, presence of microacanthostyles on the reverse colony surface, and smaller autozooecial apertures. R. microretiformis n. comb. has thinner and more closely spaced branches. R. araxensis n. comb. is similar to R. accurata (Trizna, 1950) differing from it in having thicker branches (0.26-0.34 vs. 0.20-0.25 mm in R. accurata ).

REMARK

Fenestella araxensis is placed in the genus Rectifenestella because of its pentagonally shaped autozooecial chambers in the middle tangential section and presence of singular row of nodes on the keel ( Morozova 1974: 61).

Figures

FIG. 4. — A-E, Dyscritella leptosa n. sp.; A, SMF 2111, holotype, longitudinal section through the cylindrical colony; B, paratype 23- 6-10, cross section through the cylindrical colony; C, paratype 23-6-10, cross section through the encrusting colony; D, holotype 17-1-4, longitudinal section through the cylindrical colony;E, holotype 17-1-4, tangential section;F-H, J, Rectifenestella crassinodata n. sp.; F, SMF 2113,holotype,tangential section displaying apertures with apertural nodes;G, SMF 2113, holotype,tangential section displaying apertures and carinal nodes; H, 1-5-2, deep tangential section displaying autozooecia; J, 23-1-1, tangential section; I, K, L, Rectifenestella araxensis (Nikiforova,1933) n. comb.; I, 1-4-3, deep tangential section displaying autozooecia;K, 17-1-6, tangential section displaying apertures and carinal nodes; L, 1-4-1, deep tangential section. Scale bars: A, C, K, L, 0.5 mm; B, 1 mm; D, F, 0.2 mm; E, H, I, 0.1 mm; G, 0.25 mm; J, 2 mm

FIG. 5. — A-E, Rectifenestella araxensis (Nikiforova,1933) n.comb.;A, 7-1-1, thin section of reverse surface showing abundant microacanthostyles; B, 17-1-6, tangential section showing apertures with apertural nodes and carinal nodes; C, 9-5-7, cross section of the branch showing autozooecial chambers; D, 1-4-3, tangential section of the branch with three rows of autozooecia; E, 1-4-1, deep tangential section of the branch with three rows of autozooecia and dichotoming branch;F-I, Rectifenestella microretiformis (Morozova, 1970) n. comb.; F, 23-1-2, deep tangential section; G, 7-2, thin section of the reverse surface showing abundant microacanthostyles; H, 10-1-6, tangential section; I, 7-2-3, tangential section. Scale bars: A-C, F, 0.1 mm; D, E, 0.5 mm; G, 0.2 mm; H, I, 0.25 mm.